/*
 * Copyright (C) 2005 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * DEPRECATED.  DO NOT USE FOR NEW CODE.
 */

#ifndef ANDROID_SHARED_BUFFER_H
#define ANDROID_SHARED_BUFFER_H

#include <atomic>
#include <stdint.h>
#include <sys/types.h>

// ---------------------------------------------------------------------------

namespace android {

    class SharedBuffer
    {
    public:

        /* flags to use with release() */
        enum {
            eKeepStorage = 0x00000001
        };

        /*! allocate a buffer of size 'size' and acquire() it.
         *  call release() to free it.
         */
        static          SharedBuffer*           alloc(size_t size);

        /*! free the memory associated with the SharedBuffer.
         * Fails if there are any users associated with this SharedBuffer.
         * In other words, the buffer must have been release by all its
         * users.
         */
        static          void                    dealloc(const SharedBuffer* released);

        //! access the data for read
        inline          const void*             data() const;

        //! access the data for read/write
        inline          void*                   data();

        //! get size of the buffer
        inline          size_t                  size() const;

        //! get back a SharedBuffer object from its data
        static  inline  SharedBuffer*           bufferFromData(void* data);

        //! get back a SharedBuffer object from its data
        static  inline  const SharedBuffer*     bufferFromData(const void* data);

        //! get the size of a SharedBuffer object from its data
        static  inline  size_t                  sizeFromData(const void* data);

        //! edit the buffer (get a writtable, or non-const, version of it)
        SharedBuffer*           edit() const;

        //! edit the buffer, resizing if needed
        SharedBuffer*           editResize(size_t size) const;

        //! like edit() but fails if a copy is required
        SharedBuffer*           attemptEdit() const;

        //! resize and edit the buffer, loose it's content.
        SharedBuffer*           reset(size_t size) const;

        //! acquire/release a reference on this buffer
        void                    acquire() const;

        /*! release a reference on this buffer, with the option of not
         * freeing the memory associated with it if it was the last reference
         * returns the previous reference count
         */
        int32_t                 release(uint32_t flags = 0) const;

        //! returns wether or not we're the only owner
        inline          bool                    onlyOwner() const;


    private:
        inline SharedBuffer() { }
        inline ~SharedBuffer() { }
        SharedBuffer(const SharedBuffer&);
        SharedBuffer& operator = (const SharedBuffer&);

        // Must be sized to preserve correct alignment.
        mutable std::atomic<int32_t>        mRefs;
        size_t                      mSize;
        uint32_t                    mReserved[2];
    };

    static_assert(sizeof(SharedBuffer) % 8 == 0
                  && (sizeof(size_t) > 4 || sizeof(SharedBuffer) == 16),
                  "SharedBuffer has unexpected size");

// ---------------------------------------------------------------------------

    const void* SharedBuffer::data() const {
        return this + 1;
    }

    void* SharedBuffer::data() {
        return this + 1;
    }

    size_t SharedBuffer::size() const {
        return mSize;
    }

    SharedBuffer* SharedBuffer::bufferFromData(void* data) {
        return data ? static_cast<SharedBuffer *>(data)-1 : 0;
    }

    const SharedBuffer* SharedBuffer::bufferFromData(const void* data) {
        return data ? static_cast<const SharedBuffer *>(data)-1 : 0;
    }

    size_t SharedBuffer::sizeFromData(const void* data) {
        return data ? bufferFromData(data)->mSize : 0;
    }

    bool SharedBuffer::onlyOwner() const {
        return (mRefs.load(std::memory_order_acquire) == 1);
    }

}; // namespace android

// ---------------------------------------------------------------------------

#endif // ANDROID_VECTOR_H
